Question

You need a buffer to keep a solution a pH of 9. why do you need ammonia as your buffer?

Answer 1

because its buffer range is suitable for pH 9

Answer 2

what is ammonia? weak acid or base? and why would you need either an acid or base to keep it at 9?

Answer 3

ammonia is NH3 which in liquid solution gives NH4OH so it is basic, point of buffer is to keep pH stable at certain pH weather you add acid or base

Answer 4

so to keep a ph of 9, why do you need to add an acid or base?

Answer 5

you dont need to add acid or base, buffers are solutions of bases or acids and their salts, their purpose is to keep pH at certain value

Answer 6

but the entire question is " You need a buffer to keep a solution at a pH of 9. You have the following chemical avaliable to you: nitric acid, phosphoric acid, potassium hydroxide, and ammonia. Which one would you choose? Explain your answer.

Answer 7

and hi again, sorry my manners :)

Answer 8

you would use ammonia cause it is only base from that list

Answer 9

so why a base then?

Answer 10

wouldnt base make the solution make it higher pH?

Answer 11

cause you need buffer pH 9 and basic part of the scale is 7-14

Answer 12

sorry, i don't understand...

Answer 13

you dont understand cause you obviously havent read and learned basics of chemistry... this isnt too hard to understand, you need basic pH and you are given acids and one base and you ask why would you use base to make base buffer....

Answer 14

but wouldnt a base higher the ph?

Answer 15

i understand that the others are acids and there is only one base, but a base wouldn't keep the ph, i would only think if something was weak would work as a bufer

Answer 16

that was rather rude, kryten. i dont know half of that.

Answer 17

ok lets start from the begining....
first! you need to prepare buffer
second! buffer needs to have pH 9
third! you are given acids and one base for choice to make that buffer
fourth! you choose base cause you need basic buffer
fifth! buffer is solution of base and its salt
sixth! when you make that solution you have your buffer
seventh! your buffer now has pH 9
eight! now if you add certain amount of acid or base pH will stay at pH 9

Answer 18

hello2 that are basics, to learn that you need to open book and learn it, there is no other way, not knowing that means you havent studied...

Answer 19

maybe it just doesnt make sense...

Answer 20

it might make more sense if someone stated the purpose of a buffer!

Answer 21

OHHH... so a buffer isn't trying to make a ph of 7... and sorry we havnt larned much about buffers... so the buffer is just trying to make a ph of whatever, so that whenever you add any solution to it, it would stay a pH of 9. i see now...

Answer 22

yeah... i just didn't know the purpose of a buffer, i just know that it is supposed to keep the pH of something the same... we only got the definition. anyway, so it is to keep the SAME pH

Answer 23

yes

Answer 24

not just to get to 7...

Answer 25

no it is to keep pH of wanted value it can be 1 , 3, 13, 2.5 or any other,

Answer 26

ahh, i see... because when my teacher talked about equilibrium i thought about 7, which is the neutral , so ok i see

Answer 27

But there are two bases in you list. KOH is also a base, but in order to get a buffer, you need the presence of the two partners of an acid/base couple in the solution.

So you have to aim for a weak acid or a weak base with pKa as close as possible to the wanted pH of your buffer solution.

In that list, ammonia is the base partner in the couple NH4+/NH3.
Its pKa is 9.2, so it is extremely suitable for a buffer of pH = 9